The present invention relates to the web-forming section, that is, the former section of a paper machine, board machine, tissue machine or the like. More specifically, the invention concerns a loading device for supporting and dewatering a web-forming wire of a paper machine or the like.
Several different wire supporting and dewatering components are used in the web-forming sections of a paper machine or the like. The main purpose of these components is to generate a compression pressure and pressure pulsation in the fiber layer to be formed, to thereby promote the removal of water from the web to be formed, and at the same time contribute to the formation of the web.
With regard to know arrangements for web-forming components, general reference is made to the applicant""s FI patent publication 90 673, which discloses a two-wire web-forming section of a paper machine which includes a carrying wire and a covering wire. The carrying wire and covering wire together define a two-wire forming zone. In this forming zone is fitted a forming unit including a forming table and a dewatering box which generates a vacuum for removing water from the wire. The dewatering box includes a set of spaced ribs upon which the wire travels. During operation an upper one of the wires rests against the ribs and water is removed from the web by the dewatering box through the spaces defined between the rib elements.
Reference is also made to the applicant""s patent publication FI 95935 which relates to a rib construction for a draining device in a paper machine. Specifically a rib construction is disclosed in which a loading rib is used to support and/or load a wire in a paper machine to doctor water from the face of the wire or wires. The rib is loaded by means of a pressure medium. Between the rib and its frame part, a pressure space is formed and defined by a flexible belt. The pressure medium is introduced into the pressure space defined by the flexible belt thereby loading the rib against the wire.
Reference is further made to patent publication FI 100543 which relates to a ledge for resiliently supporting a drainage wire of a paper machine. The ledge disclosed includes a head ledge which is structured and arranged across the direction of travel of the wire so the wire can slide over said ledge as the wire travels. The head ledge is rigidly connected to a movable support ledge which also extends across the direction of travel of wire and is guided on a stationary support structure. Between the movable support ledge and the stationary structure there is a resilient push device which can displace the movable support ledge together with the head ledge between a position of rest away from the wire and an operating position in which the head ledge is pressed with a predetermined force against the wire. The stationary structure has several guide arms distributed over the length of the support ledge which are the exclusive means for guiding the movable support ledge. Several guide arms arranged in pairs are provided which grip around the support ledge in the manner of a clamp.
It has been a problem in known state-of-the-art loading devices that jamming of the loading member of the loading device can occur as a result of which more power is needed to make loading member move. As the loading member presses against the wire, the loading member is subjected to a torque as a result of the wire movement, which torque causes the above-mentioned jamming of the loading member. In order to overcome the jamming of the loading member a strong force must be applied to loading device. This problem is harmful to formation of the web, because the loading force placed on the wire via the loading member cannot be accurately controlled. Thus, it is a common problem that the loading member either applies too much pressure or too little pressure to the wire resulting in said web formation problems.
It is an object of the present invention to provide a loading device which overcomes the short comings of the prior art arrangements discussed above.
The present invention is based on the new and inventive idea that in order to prevent the jamming phenomenon of the loading member, a pivoting roller or rollers or balls are arranged between the loading member of the device and the base member of the device, which will prevent occurrence of said jamming problems.
According to one especially advantageous embodiment of the invention, such a roller is fitted to the top end of the base member of the loading device, the periphery said roller being arranged so that it abuts a portion of the loading member so that it can move in an up and down fashion relative to the base member.
According to another advantageous embodiment of the invention, a pin is fitted to the top end of the base member of the loading device and, correspondingly, a ball bushing is arranged within the loading member, whereby the pin will roll along the balls of the ball bushing.